Field of the Invention
The present invention relates to an image capturing apparatus and a control method for an image capturing apparatus.
Description of the Related Art
Conventionally, a technique for realizing high-speed phase difference AF that eliminates the need for a dedicated AF sensor by applying a subject image phase difference detection function to pixels included in an image sensor has been disclosed. In Japanese Patent Laid-Open. No. 2000-292686, a pupil division function is applied in a portion of light, receiving elements (pixels) of an image sensor by decentering sensitive regions of light receiving portions with respect to an optical axis of one on-chip microlens. Then, by arranging these pixels as focus detection pixels at a predetermined interval between imaging pixel groups, phase difference focus detection is performed based on signals obtained from the focus detection pixels.
Note that with this kind of image capturing apparatus, the captured image generated based on the output from the imaging pixel groups is usually displayed as a through-the-lens image on a display apparatus included, on the image capturing apparatus. For this reason, with consideration given to the fact that the image is to be displayed, exposure control is performed such that the average exposure amount of the entire image is suitable.
On the other hand, Japanese Patent Laid-Open No. 2000-292686 discloses a technique in which a removable half-mirror is provided on an optical path between an imaging optical system and an image sensor and focus detection is performed based on a light flux from a subject that is incident on the image sensor via the half-mirror at the same time as monitoring via an optical finder is made possible.
When the half-mirror is inserted into the optical path between the imaging optical system and the image sensor and a subject is monitored through the optical finder, the amount of incident light from the subject is limited by only the aperture opening of the lens, and therefore the full-open state is usually maintained. For this reason, exposure control using the aperture cannot be performed, and depending on the brightness of the subject, the pixel signals become saturated relatively easily.